Different threshold voltage levels map to different bits in nonvolatile memories. Due to noise, the actual threshold voltage levels for each state within a group of cells follow a distribution. Controllers of the nonvolatile memory will model the threshold voltage distribution of each state. Conventional controllers use a parametric model for a “flash channel”. The flash channel parameters change with use conditions, such as program/erase cycles and retention. Therefore, the controllers track the channel parameters over time. However, the tracking operations consume bandwidth to the memory and utilize storage space for maintaining the channel parameters.
It would be desirable to implement a flash channel parameter management with read scrub.